There are four layers, including top, power, ground and bottom.
My way of grounding:
I follow the instruction by Maxim: https://www.maximintegrated.com/en/app-notes/index.mvp/id/5450
As it introduces, there is no need for a cut in ground plane. Since the return currents from analog circuits will not overlap with the return currents of digital circuits. And the high frequency currents will be absorbed by the small capacitors.
However, we recently hired a very professional consultant company to help us design a newer version. They design in a different way.
The consultant way
They cut the ground plane into two: analog and digital. And connect the two planes with 0 Ohm resistors when necessary. They are very professional, so I start to think in their ways.
What I think their way could be good: Without cutting, the digital return currents still have the chance going into the analog ground.
What I think may be bad: There could be several connections between the analog ground and digital ground. There would be ground loops and become antenna.
Could I have comments here?